1. Field of the Invention
The present invention relates to a process for producing a polyhydric alcohol by reacting an aliphatic aldehyde with formaldehyde which alcohol is useful as a raw material for polyester resins, alkyd resins, polyurethane resins, polycarbonate resins, plasticizers, surfactants, lubricating oils, basis for cosmetics, reactive monomers and the like.
2. Description of the Related Arts
There is described, as a process for producing a polyhydric alcohol, a two-stage reaction process in which an aliphatic aldehyde and formaldehyde are subjected to an aldol condensation reaction, and subsequently to a crossed Cannizzaro reaction each in the presence of a base catalyst, in Japanese Patent Application Laid-Open Nos.139141/1988 (Sho 63), 162538/1983 (Sho 58), etc., said aliphatic aldehyde being represented by the following formula (I): ##STR1## wherein R is a hydrogen atom or a straight-chain or branched aliphatic hydrocarbon group having 1 to 4 carbon atoms.
The above-mentioned two-stage reaction process is based on the premise that the objective polyhydric alcohol is produced in combination with a formic acid salt. Examples of the base catalyst to be used in said process include a hydroxide of any of alkali metals and alkaline earth meals and a carbonate of any of the above-mentioned metals. The catalyst is exemplified by sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, calcium carbonate, and tertially amines such as trimethylamine, triethylamine, and tributylamine.
In general, a base catalyst comprising sodium hydroxide or calcium hydroxide is used in the process for producing a polyhydric alcohol by the reaction of an aliphatic aldehyde with formaldehyde. However, in order to obtain an objective polyhydric alcohol in high selectiyity in the presence of the base catalyst comprising sodium hydroxide or calcium hydroxide, it is necessary to use formaldehyde in a large excess against the aliphatic aldehyde. In addition, in the case where such a large excess of formaldehyde is used, unless the reaction is carried out in a reaction system diluted with water, large amounts of byproducts are formed, thereby making it impossible to obtain the objective polyhydric alcohol in high selectivity.
There is also known a process for the production of a polyhydric alcohol by two-stage reaction process in which an aliphatic aldehyde and formaldehyde are subjected to an aldol condensation reaction, and subsequently to a crossed Cannizzaro reaction each in the presence of a carbonate catalyst. The process, however, leads to the by-production of about 10 mol % of 2-alkenals that are low in added values. Thus in order to suppress the by-production, it is also necessary to use formaldehyde in a large excess against the aliphatic aldehyde.
The aforestated process that uses a large excess of formaldehyde involves the problem such that the production process is made intricate, since it is required to recover the used excess of formaldehyde from the viewpoints of economy and the influence of wastes and the like upon the environment.
In view of the above, a general object of the present invention is to provide a process for producing a polyhydric alcohol by subjecting an aliphatic aldehyde and formaldehyde to an aldol condensation reaction, and subsequently to a crossed Cannizzaro reaction, which process is characterized in that the objective polyhydric alcohol is produced in high selectivity using a slight excess of formaldehyde against the theoretical molar amount of the aliphatic aldehyde without dilution of the reactants with water.